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Role of boundary conditions, topology, and disorder in the chiral magnetic effect in Weyl semimetals

机译：边界条件，拓扑和无序在Weyl半金属手性磁效应中的作用

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Quantum field theory predicts Weyl semimetals to possess a peculiar response of the longitudinal current density to the application of a DC magnetic field. This peculiar response, known as the chiral magnetic effect (CME), has been proposed as one of the signatures of the unique chiral anomaly of Weyl nodes. Here we show that such a response can in principle exist in a model without Weyl nodes. On the other hand, such a CME is at odds with a general result showing the vanishing of the bulk current in an equilibrium system on any real material with a lattice in an external magnetic field. Here we resolve this apparent contradiction by introducing a model where a current flows in response to a magnetic field even without Weyl nodes. We point out that the previous derivation of a vanishing CME in the limit of vanishing real frequency is a consequence of the assumption of periodic boundary conditions of the system. Consistent with recent work, we found the finite frequency CME to be nonvanishing in general when there was a nonvanishing Berry curvature on the Fermi surface. This does not necessitate having a topological Berry flux as in the case of a Weyl node. Finally, we study how the perturbation theory in magnetic field might be more stable in the presence of disorder. We find that in a realistic disordered system, the chiral magnetic response is really a dynamical phenomena and vanishes in the DC limit.
机译：量子场论预测Weyl半金属对直流磁场的施加具有纵向电流密度的特殊响应。这种独特的反应被称为手性磁效应（CME），已被提出作为Weyl节点独特的手性异常的特征之一。在这里，我们证明了这种响应原则上可以存在于没有Weyl节点的模型中。另一方面，这样的CME与显示在外部磁场中具有晶格的任何真实材料上的平衡系统中的大电流消失的一般结果不一致。在这里，我们通过引入一个模型来解决这一明显的矛盾，在该模型中，即使没有Weyl节点，电流也会响应磁场而流动。我们指出，先前消失的CME在真实频率消失的极限中的推导是假设系统存在周期性边界条件的结果。与最近的工作一致，我们发现当费米表面上的贝里曲率不消失时，有限频率CME通常不会消失。与Weyl节点的情况一样，这不必具有拓扑Berry通量。最后，我们研究了在无序情况下磁场中的微扰理论可能会更稳定。我们发现，在一个现实的无序系统中，手性磁响应实际上是一种动力学现象，并且在直流极限内消失。

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  • 来源
    《Physical review》 |2016年第11期|115160.1-115160.10|共10页
  • 作者

    Yahya Alavirad; Jay D. Sau;

  • 作者单位

    Department of Physics, Condensed Matter theory center and the Joint Quantum Institute, University of Maryland College Park, Maryland 20742, USA;

    Department of Physics, Condensed Matter theory center and the Joint Quantum Institute, University of Maryland College Park, Maryland 20742, USA;

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